<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>a+</title>
</head>
<body>
    <script>
        var a,b,c;
        a=5;
        b=7;
        (c=a,a=b,b=c);
        console.log(a,b);
        console.log((a++)+(--b))
    </script>
</body>
</html>